Cardiovascular disease is the leading cause of death for Americans, and advancing age confers major risk despite control of traditional risk factors. Age-related increases in vascular arterial stiffness and endothelial dysfunction precede clinical disease and are early independent predictors of atherosclerosis, hypertension, and cardiovascular events. Interactions between these age-related increases and other lifestyle risk factors likely exacerbate vascular aging and cardiovascular disease development. Habitual diet is a lifestyle factor that influences cardiovascular risk, and numerous studies have reported that foods and dietary patterns affect arterial stiffness and endothelial dysfunction. However, the extent to which habitual diet moderates the effect of age on these measures of vascular health is unknown. The aim of this research is to examine the effect of diet quality, as defined by public health recommendations, on arterial stiffness and endothelial dysfunction in a large cross-sectional sample of adults from the Framingham Heart Study. We will also investigate whether diet quality moderates the effect of age on vascular health. Arterial stiffness, endothelial dysfunction, and habitual diet were previously assessed in approximately 7000 participants of the Framingham Offspring Cohort and the Third Generation Cohort. Carotid-femoral pulse wave velocity and brachial flow-mediated dilation were used to index arterial stiffness and endothelial dysfunction, respectively. Habitual diet was determined via food frequency questionnaires, and diet quality will be quantified using the Dietary Guidelines Adherence Index. Multiple regression will be used to evaluate the association between diet quality and the age-diet quality interaction with arterial stiffness and endothelial dysfunction, independent of potential clinical confounds (e.g. sex, body mass index, blood pressure, smoking, other medical conditions). Exploratory analyses will seek to determine which components of the Dietary Guidelines are associated with the greatest protection from age- related arterial stiffness and endothelial dysfunction. The findings from the current proposal may suggest a link between diet quality, arterial stiffness, and endothelial dysfunction, and as such will be useful for designing interventions to treat or prevent age-related vascular decline.